A 360-degree toothbrush as described in Patent Document 1 has been known as a kind of a toothbrush. This toothbrush has a cylindrical radial brush head at the tip portion of the brush handle, and such a brush head can be manufactured by using a method, for example, described in Patent Document 2.    Patent Document 1: Japanese Patent Application Laid-Open No. H9-168427    Patent Document 2: Japanese Patent Application Laid-Open No. 2003-220080
By the method described in Patent Document 2, a disk-shaped radial vane, in which a plurality of bristle members extend outward from the center part in the radial direction of the disk shape, is manufactured, and the vanes are mounted to the tip portion of the brush handle sequentially so as to be superposed, whereby a cylindrical radial brush head is manufactured. The following explains the method of manufacturing a radial vane described in Patent Document 2 with reference to FIGS. 19 to 23.
As shown in FIG. 19, a manufacturing apparatus includes a bristle opening jig d disposed on a processing bed b, a bristle presser e, a welding head f, and a press-cutting punch g. The processing bed d has a through hole through which a bristle bundle a formed by bundling bristle members of a predetermined number penetrate, and has a bristle lifting chuck c disposed thereunder. The bristle opening jig d is combined with the annular-shaped bristle presser e concentrically. The bristle opening jig d and the bristle presser e, the welding head f, and the press-cutting punch g are selectively conveyed to a position right above the through hole of the processing bed b by a driving mechanism that is not shown in the drawings.
In operation, as a first step, the bristle bundle a penetrating the through hole of the processing bed b is pushed up from the under side by the bristle lifting chuck c provided below the processing bed b, and so as to be exposed on the processing bed b by a predetermined length.
In a second step, as shown in FIG. 20, the bristle opening jig d, the lower end face of which is formed conically, is pressed to the center part of the exposed part of the bristle bundle a, thereby opening the exposed part to the periphery. In a third step, as shown in FIG. 21, the annular-shaped bristle presser e combined to the outside of the bristle opening jig d is lowered so as to be pressed against the bristle members which are half-way opened, thereby completely opening the exposed part of the bristle bundle a to the periphery.
In a fourth step, as shown in FIG. 22, with the exposed part of the bristle bundle a being opened radially with the bristle presser e, the bristle opening jig d is lifted and evacuated to a side. Instead, the welding head f is moved to a position right above the through hole and is lowered so as to weld the center part of the bristle members, opened radially, in an annular shape. Finally, in a fifth step, as shown in FIG. 23, the welding head f is lifted and evacuated to a side, and instead, the press-cutting punch g is moved to a position right above the through hole and lowered, thereby separating and removing the inner side of the annular-shaped weld portion.
In this way, the disk-shaped radial vane is manufactured. The manufactured radial vane has a through hole, in the center part thereof, through which the tip portion of a brush handle penetrates, an annular-shaped weld portion provided around the through hole, and further, a plurality of bristle members extending outward from the weld portion in a radial direction (brush portion). A plurality of vanes are fitted and fixed to the tip portion of the brush handle so as to be superposed, whereby a 360-degree toothbrush having a cylindrical radial brush head at the handle tip portion is manufactured.
A 360-degree toothbrush manufactured in this way has no directionality in the peripheral direction of the brush handle, and has a characteristic that it is easy even for elderly persons or children to use this toothbrush. Further, it is very suitable for massaging gums or removing coat of tongue. On the other hand of such characteristics, there are also the following problems.
In the brush head formed by superposing a plurality of radial vanes manufactured by the method described in Patent Document 2, the bristle density becomes too high, especially in the axial direction, and this causes, in addition to the unpleasant sense of use, hurting gums, mucous membrane of mouth and enamel. Moreover, since the radial vanes are too close, there are such problems that the air permeability is deteriorated, which is not desirable in the hygiene point of view, and that it is hard for the tips of the bristles to be inserted between teeth.
In order to solve these problems, small annular-shaped spacers have been employed to be fitted between the radial vanes alternatively when superposing the vanes, thereby reducing the bristle density in the axial direction on purpose. However, a rise in cost due to increases of the number of components and of assembling works by using the spacers has been noted as a problem of great importance. In addition, there has also been a problem that the deterioration in hygiene is caused because of contamination of foreign materials when inserting the spacers and an increase in clearances due to spacers provided between the vanes.
Further, there is another problem of complication since it is necessary to use a plurality of tools appropriately in order to complete a radial vane. That is, independent steps using different tools are required, such as pressing and opening of the bristle bundle a by the bristle opening jig d, fixing by the bristle presser e, welding by the welding head f, and removing of the center part by the press-cutting punch g, and there are a large number of steps involved. This has prevented the productivity from increasing, and thus caused a problem that the price of a product becomes expensive.